Recently, prices of the petrochemical fuel keep going up, and a use of the petrochemical fuel in power generation would result in the greenhouse effect, which destroys the ecological environment. Therefore, every country starts to seek some alternative energies without destroying the earth. Undoubtedly, the renewable energy, such as wind energy, solar energy, ocean energy and water power, etc., is one of the best choices of the alternative energy. The ocean energy includes tidal energy, ocean thermal energy and offshore wind energy.
Please refer to FIG. 1, which is a diagram showing a conventional system integrating a tidal power generation device and a wind power generation device. The system 10 integrating the energies produced by the tidal power generation device and the wind power generation device is provided in Taiwan Patent No. I307995, which includes a dam 101, a tidal pool 102, a valve 103, a water turbine 104, a tide switching device 105, a transmission mechanism 106, an orienting device 107, a generator 108, a holder 109, a wind turbine 110, and the ocean 111.
The dam 101 surrounds the tidal pool 102, and the valve 103 and the water turbine 104 are disposed on the dam 101. The valve 103 can be operated to cause the water in the tidal pool 102 to flow toward the ocean 111, or cause the water in the ocean 111 to flow into the tidal pool 102 so as to activate the water turbine 104. The dam 101 can be used as a base of the wind power generation system. The holder 109 is disposed on the dam 101, and the wind turbine 110 is disposed on the holder 109 to drive the generator 108 to generate the power, whereby achieving the purpose of using the tide and wind power generation devices.
The tidal power generation device is one of important developments in capturing ocean energy. When the tide is used to generate power, the tide would induce a vertical water level difference and a horizontal movement of the ocean. A use of the vertical water level difference of the ocean in power generation is known as tidal difference power generation, while a use of the horizontal movement of the ocean in power generation is known as tidal current power generation. The tidal current power generation can be achieved by only setting a marine-current power generator in the ocean to get the kinetic energy of the ocean and convert it into electric power. Currently, the developed tidal current turbine is classified as a horizontal turbine and a vertical turbine according to whether the rotating shaft of the turbine is parallel or perpendicular to the sea level.
In 2009, Yuen at al. disclose a combination of a vertical tidal current turbine collocated with a permanent magnet generator with a low speed to be used in a tidal current power generating system. In the disclosure, it is described that if the tidal current turbine is controlled at a best rotating speed corresponding to the respective flowing speed of the tidal current, the turbine would operate in a best tip speed ratio, so that the turbine could make it possible to get the largest mechanical power at the flowing speed of the tidal current. In the disclosure, three different frameworks of vertical tidal current turbine are provided, and the steady state analyzing results of the three kinds of vertical tidal current turbines are compared to another when they are collocated with the permanent magnet generator with a low speed at different rotating speeds and different loadings. At the end of the disclosure, the authors analyze the rotating speed limitation and the temperature limitation of such tidal current power generation framework by using different software, and demonstrate that such tidal current power generation framework would not go beyond the limitations to cause damage to the machine when operating in a normal working range.
In 2009, Yao et al. disclose a hybrid renewable energy system including the offshore wind farm and the tidal current farm. In the disclosure, a dynamic model and a controlling framework of the renewable energy system are provided. The authors use the turbine to directly drive a permanent magnet generator for generating electric power, and conclude a model of the perpendicular axis (rotor reference axis) of the permanent magnet generator in the disclosure. It is also mentioned in the disclosure that a rectifier controlled by the pulse width modulation (PWM) can be used to control the rotating speed of the rotor of the generator, so as to achieve a purpose of tracking maximum power. At the end of the disclosure, the authors construct a simulated model by using MATLAB/Simulink software to demonstrate the possibility of the system provided thereby.
Conventional tidal power generation device transfers a linear movement to a rotating movement via the ways such as crank and crank shaft, and connects to a rotating type generator by increasing rotating speed via a gear box. Such a power generation scheme would result in loss of energy due to the intermediate energy change.
A tidal power generation device different from the conventional one, an integration of tidal power generation and wind power generation, and the power control thereof are provided in the present application.